U.S. President Joe Biden meets the leaders of Sweden and Finland on Thursday after the nations set aside their long-standing neutrality and moved to join the NATO alliance in response to Russia’s invasion of Ukraine.

Hours before his first trip to Asia as president, Biden will sit down with Swedish Prime Minister Magdalena Andersson and Finnish President Sauli Niinistö at the White House to discuss their NATO applications.

“This is a historic event, a watershed moment in European security. Two nations with a long tradition of neutrality will be joining the world’s most powerful defensive alliance,” said White House national security adviser Jake Sullivan.

Biden has made uniting Europe against Russia’s invasion of Ukraine a top priority. Turkey has raised questions about including Finland and Sweden in the alliance, asking Sweden halt support for Kurdish militants it considers a terrorist group and both to lift their bans on some sales of arms to Turkey.